This application relates to holographic optical elements, and more particularly, to color filter arrays and microlens arrays formed from holographic optical elements for use in radiation sensor arrays.
Semiconductor radiation sensors can be fabricated on a common semiconductor substrate to form a sensing array. Each radiation sensor is responsive to radiation to produce an output that is a measurement of the amount of received radiation. An input optical device, such as a lens array or an optical filter array, may be placed in the input optical path of the input radiation to control or manipulate the input radiation in order for the input radiation to be properly received by the sensor pixels of the sensing array.
This application includes designs and techniques for using holographic optical elements to form an optical mask layer for modifying input radiation to a sensor array. Each holographic optical element is spatially associated with a sensor pixel of the sensor array and may be formed on top of a sensor or buried in the pixel layers of each sensor. The holographic optical elements may be optically reflective, absorptive, refractive, or diffractive in nature when interacting with input radiation.
In one implementation, holographic optical elements of the optical mask layer are designed as micro lenses to respectively focus input radiation into their respective sensors. In another implementation, holographic optical elements of the optical mask layer are designed as a color filter array where each holographic optical element filters different spectral bands of received radiation for a color sensing array. For example, each holographic optical element may be an optical grating that separates input radiation into different beams at different wavelengths to different directions. The grating patterns are designed to direct the beams at different wavelengths to different adjacent sensors to produce color images.